Black hole Definition and 999 Threads

The question is as follows: suppose I throw a metal bar 1m long inside the event horizon of a supermassive black hole of 1 million solar masses. At both ends of the metal bar there is a light source. (I chose a supermassive black hole to rule out any spaghettification process: with some quick...

I've recently read a new article that said that the recent gravitational waves might have had 2 black holes in a star that gave me a question, because you need masses to move or accelerate to generate gravitational waves, what happens to the mass inside of the star? because black holes's space...

I refer to the time coordinate of an outside observer (ideally hoovering over the BH at large constant distance). Can (s)he actually see something falling into the hole within finite time, that means actually disappearing and making the Event horizon larger? If no, all the merging of black...

According to the holographic principle, It is proposed that the entire information that is kept in a 3D volume of the black hole can be represented in a 2D surface of its horizon. What if we have a drunk falling into a black hole and moves in a random walk in his inertial frame. According to the...

(1) Maybe should've messanged this, but given LIGO, the FAQ might need a light edit. It says, "Gravitational waves have never been detected directly, but the loss of energy from the Hulse-Taylor binary pulsar has been checked to high precision against GR’s predictions of the power emitted in...

light waves created inside a black hole cannot. Can gravitational waves escape from inside of black holes? in classical GR. does the answer change in string theory?

Hi Folks, Can somenone explain what "information" is with respect to black holes? I thought it was all about mass and energy from both quantum Mechanics and GR perspective. Why does "information" come into it...sounds unusual to say the least. Thanks B

This question is in context of the recent gravitational wave detection by aLigo. Apparently aLigo has detected the entire process, including the before merger, during merger, and aftermath of the completed merger. My understanding is that two black holes should not be seen to be merging in...

http://cdn4.sci-news.com/images/2016/02/image_3628-Gravitational-Waves.jpg In the above image, i can see that the event horizon of each black hole has decreased in size. Does that mean that the event horizon can shrink in the presence of another black hole?

And how does graviton escape the event horizon? People say it's because those gravitons are "virtual particles" and can travel faster than light, yet many of the posts i read on here say virtual particles don't even exist. Also, gravity TRAVELS at the speed of light, if the sun is suddenly gone...

This picture confuses me. It showed here that the red particle at top right get suck into the black hole. But to a distant observer, everything near the black hole get time dilation and finally freeze at the horizon, right? So, "when" the black hole evaporates? Moreover, why the black hole likes...

Hi. From an outside observer's view, any object approaching the event horizon of a black hole appears to slow down and never quite pass through the horizon. So information about those objects can always be retrieved (if you correct for the redshift). So what actually is the information paradox...

Hi. Charge is one of the few properties a black hole can have. EM interaction is mediated by photons. How can they escape the BH?

Would it be possible that you could create a black hole from heating something really hot. I heard Vsauce said if you heat something hot enough that it's wave length of the light released is smaller than the plank length, it would become a black hole. That means that the energy would be on the...

Is this the proper formula for calculating the Schwarzschild radius of a black hole? rs = 2GM / c2 If it is not, or if anyone has one that might work better, could you refer it to me?

I'm not talking about white holes. Indeed, the big bang as the explosion of a black hole are an explosion of singularity.

Hello, I'm working on a hypothetical situation involving a planetary body orbiting a black hole (similar to the scenario in Interstellar, but for different reasons), trying to balance tidal forces with orbital distance and time dilation. First, I'm interested in the effect of gravitational...

[I originally posted this in Astronomy and Astrophysics but it didn't get much traction. Perhaps folks in this forum would have something to contribute...] [FONT=Georgia]I'd like to understand if and when information is ever actually lost in a black hole; specifically, I'd like to analyze the...

This paper; http://arxiv.org/abs/1601.05473, The Early Growth of the First Black Holes discusses the evolution of supermassive massive black holes [SMBH] as inferred from observations of high z quasars: which has provoked questions about the putatitve age of the universe and the time it allows...

[FONT=Georgia]I'd like to understand if and when information is ever actually lost in a black hole; specifically, I'd like to analyze the statement: Is there information, which existed in the past, that is theoretically unavailable to external observers today due to falling through the event...

Hi. Now that I understand the conservation law of angular momentum, and given the fact that c is constant, I infer that if a photon were to go into orbit around a black hole, it could only take a circular orbit. No elliptical orbits for photons, because if it were to follow an elliptical orbit...

I have just seen a brief clip of an article by a journalist regarding a lecture given by Hawking this week about the mystery of where information of a star goes to when it is swallowed by a black hole. As a non physicist, I am grappling with what exactly is meant by this. Isn't this just a...

Since the center of a black hole is defined as a singularity and space-time collapses at that point (assumption) is it possible to define this point in 3D coordinates? In other words, is it possible that our universe can not be described as a 3D space but rather as a space with 2.99... dimensions?

Signature of an Intermediate-Mass Black Hole in the Central Molecular Zone of Our Galaxy - arXiv 1512.04661 (free reprint) Apparently there was another thread with a similar title ("Second black hole may lurk at Milky Way's heart") from June 2003, but it really had nothing to do with a second...

What would happen if you were to fly a starship traveling near the speed of light directly into a black hole? Would it stay in tact because it cannot be accelerating any faster? Or would it split because it's being accelerated in all directions simultaneously?

I feel like this could go in quite a few of the Physics subforums (Quantum Physics, Beyond the Standard Model, Special and General Relativity, or High Energy, Nuclear, Particle Physics) instead of Astronomy and Cosmology, but hopefully this will work. This is my first question I've posed here...

Hello! I am new to this forum, but I'll give it a shot. It is my understanding that photons have no mass- but that light is still pulled by the gravity of a black hole. How can something without a mass, and therefore, gravity, be pulled by the gravity of another object? Any insight would be...

So for an outside observer it appears someone falling into is slowing down and then gets redder and redder. But what about for the local observer? From the perspective of the person falling I would imagine that the universe would appear to speed up tremendously. Is it possible you could survive...

If a black hole had a mass similar to the Sun (I know black holes tend to be at least three times larger but let's assume an unusual series of events) how far would the are of extremely distorted bent gravity around it be could it cause closely orbiting bodies to be pulled or pushed out of orbit...

I know there are many threads about falling into black holes and I'm sorry for posting another one. I have a specific question and couldn't find the answer in prior threads, although it's possible that it's there somewhere. If A is outside the supermassive black hole and B falls into it, I know...

Hello there! I just made this account today because I figured this place would be a good way to get some answers to things that have bugged me for years. I'm not particularly sure how this would even work, so bare with me here. There is a critical density at which a black hole forms, which...

Hi everyone. First post here! It's an odd thought and relax I'm expecting to be wrong but the more I think about this the more interested I get.. Let's say you're chilling in the centre of earth, you feel no (little) pull because the gravity of Earth cancels out in all directions. If a black...

Can a Black hole also be a wormhole ?? is it possible

OK so some stars evolve into neutron stars which I assume are so small (10's of kms) because ALL empty space is removed between the atoms.. absolute highest density possible? Now.. is a black hole larger (massive and in diameter) than a neutron star and called a black hole only because the...

I was wondering, if there was a black hole in the center of a nebula, then would there be a possibility that the nebula would be eaten from the inside out before any stars could be born? It'd be something interesting to observe over time.

Homework Statement Soon astronomers will be imaging the “shadow” of light from the event horizons of black holes. Since black holes are very small, this achievement seems impossible. Nevertheless, it is possible for three reasons: 1. Supermassive black holes have large event horizons. 2. Radio...

have read numerous times about Hawking radiation. don't understand how that can lead to black hole evaporation in so much that wouldn't as many matter as anti-matter particles fall in thus balancing out over time to the growth and evaporation of black holes thus leaving the mass of the balck...

Multiple_Authors submitted a new PF Insights post Is the Universe a Black Hole? Continue reading the Original PF Insights Post.

If we have an infalling observer through the event horizon,will she see the end of the Universe?

Hi, I have often read that at large enough distances, the gravitational effect of a black hole is no different than the gravitational effect of a star or other body of the same mass. But that at close distances the difference shows up, for example the notion of the photon sphere at 1.5 times...

I was watching a video about how an observer outside a black hole would watch someone slow to a halt at the event horizon and I don't question it, as that makes sense. My first question to the Astrophysicists out there is what the observer falling into the black hole would see. It would make...

Hello. In oral exams my professor likes to ask if Alice and Bob can communicate, if Alice ist just above the event horizon of a schwarzschild black hole and Bob ist just below. He wants to hear: Communication is possible, because the event horizon is observer dependent. Only an observer...

The following equation equates relativistic mass to rest mass http://scienceworld.wolfram.com/physics/RestMass.html Does the mass caused by high velocity have gravity?

The question kind of says it all. How fast fast could a human move before Relativistic mass made him collapse into a black hole(the answerer can choose whatever mass and volume that they want for the equations).

I understand how the neutron stars are formed, and why the electron degeneracy pressure collapses as electrons are absorbed by protons, by photo disintegration. However, I'm struggling to grasp what happens when the gravity is large enough to overcome neutron degeneracy pressure. Apparently a...

So if light is "pulled" into a black hole by following the curvature of seriously bent space time. Then i question, why does it not eventually come back out the other side? If its not literally being dragged in then shouldn't it ride through the whole thing and eventually come back out? From...

http://www.blastr.com/2015-11-4/nasa-just-saw-something-come-out-black-hole-first-time-ever Saw this article and thought I'd share :) This is going to be a silly question, I'm sure, but what is the corona of a black hole? I tried to google it, but the first few pages were nothing but articles...

Dear all, As far as I understand, for a distant observer, time stands still at the event horizon of a black hole, right? In particular, nothing will ever pass the EH. Instead, everything that approaches the BH will get stuck at the EH and stay there forever from the perspective of the distant...

I have some difficulty understanding how a black hole can have both size and mass. Inside a black hole, space is infinitely warped and matter crushed into oblivion. Thus, if there is no space inside a black hole, what exactly separates the event horizon, or the black hole external boundary, from...

Consider a black hole with a radius of one light hour (as measured from outside, stationary observer), non rotating, having singularity in center, is radiating hawking radiation, and has no outside interference. Assume standard mathematical theory. Traveller A is falling towards hole from...